Due to its physical characteristics, lead is one of the most important non-ferrous metals in the world. Metallic lead and its alloys have significant applications in the mechanical industry, radioactive protection, battery industry, as well as in many other industries. In most cases, lead is found in nature in the form of sulphide minerals (galena), as well as in the form of carbonate minerals (cerusite). The aim of this work is to characterize the initial sample of cerussite, as well as its thermal decomposition. Physico-chemical characterization was done by ICP-AES and XRD methods. It was observed that the most abundant phase in the initial sample is PbCO3 (89%), while CaCO3 (7%) and PbS (4%) are present in a very small amount. Thermal decomposition of the sample was performed at a temperature of 900 °C, at a heating rate of 5 °C/min. It was established that the decomposition of PbCO3 occurs first, followed by the transformation of PbS into PbSO4, and at the very end of the process, the decomposition of CaCO3 occurs.